1. Field of the Invention
The present invention relates to a semiconductor device including a battery that can be wirelessly charged.
2. Description of the Related Art
In recent years, various electric appliances come into wide use, and a wide variety of products are put on the market. In particular, the spread of portable wireless communication devices is notable. A power supply for driving a portable wireless communication device has a built-in battery which is chargeable and power is supplied from the battery into the portable wireless communication device. As the battery, a secondary cell such as a lithium ion battery or the like is generally used. As matters now stand, the battery is charged from an AC adaptor which is plugged into a household alternating current power supply.
Further, in recent years, an individual identification technology which employs wireless communication which uses an electromagnetic field, radio waves, or the like has attracted attention as one mode of usage of wireless communication devices. In particular, an individual identification technology which employs an RFID (radio frequency identification) tag that communicates data wirelessly has attracted attention. An RFID tag is also referred to as an IC (integrated circuit) tag, an IC chip, an RF tag, a wireless tag, and an electronic tag. The individual identification technology which employs RFID tags is beginning to be made use of in production, management, and the like of individual objects, and it is expected that this technology will also be applied to personal authentication, through inclusion in cards or the like.
In addition, development is advanced recently for a contactless charging device in which a battery is charged with using a combination of a primary coil provided to a power feeder for charging the battery, and a secondary coil provided to a device including the battery (e.g., Patent Document 1: Japanese Published Patent Application No. H10-14126).